A divider divides an input clock having a first frequency so as to generate an output clock having a second frequency according to the dividing ratio. The following technology, for example, is known for a divider.
In the case of a ½ divider, a differential clock generated by an oscillator is input, and an output clock having a half frequency of the differential clock is generated, for example. Therefore the output clock of which frequency has been divided in half has a phase shift corresponding to the phase difference 180° of the differential clock, and this phase difference is 90° of the output clock of which frequency has been divided in half. The output clock having a 90° phase difference is used as a local clock of a mixer circuit of a transmitting apparatus or a mixer circuit of a receiving apparatus in radio communication, such as digital TV broadcasting and portable telephones. This mixer circuit is, for example, an orthogonal modulation circuit, an image removal circuit, and an orthogonal demodulation circuit.
The phase accuracy of the local clock used for a mixer circuit of a transmitting apparatus or a receiving apparatus has a major influence on the quality of a transmission signal or a reception signal. Therefore a divider is demanded to generate highly accurate phase difference 90° of the local clock, which is the output of the divider.